A possible reaction of ethane with chlorine:

CH₃CH₃ + Cl₂ → CH₃CH₂Cl + HCI

This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. The chain propagating step(s) is (are)

[1] Cl₂ → 2CI

[2] Cl + CH₃CH₃ ----slow → НСІ + CH₃CH₂

[3] CH₃CH₂ + Cl₂ ----fast → CH₃CH₂CI + CI

A. [1]
B. [2]
C. [3]
D.[1] and [2]
E. [2] and [3]